The History of Taxonomy

1. The History of Taxonomy Emily Javore

2. Taxonomy • Taxis: order or arrangement. • Nomos: law or science. • The practice and science of classification. • More specifically, the classification of organisms.

3. Emperor ShenNung2650 BC • The earliest known classification was in 2650 BC by Emperor ShenNung. He is known as the Father of Agriculture and Medicine in China. • Most early classifications began as lists of medical plants.

4. Early Classifications • The first classification systems often broke plants down into three groups: trees, shrubs and herbs. • Eber’s medical papyrus (Egypt 1500 BC) classified plants based on their habitats.

5. Aristotle384 BC – 322 BC HistoriaAnimalium Animals with blood – Live-bearing (humans and mammals) Egg-bearing (birds and fish) Animals without blood – Insects Shelled and non-shelled crustaceans Mollusks

6. Aristotle384 BC – 322 BC • The Great Chain of Being (Ladder of Life) Aristotle believed that creatures were arranged in a graded scale of perfection rising from plants on up to man.  He believed that species were fixed and unchanging, and this view persisted for the next two thousand years.

7. Great Chain of Being

8. Theophrastus372-287 BC • A student of Aristotle’s. • “Father of Botany” • De HistoriaPlantarum (On Plants) • De CausisPlantarum(The Causes of Plants) • Classified over 500 plants • Annual, biennial, or perennial?

9. A New Age • Because of Aristotle’s profound influence, there was little innovation made within taxonomy until the 16th century. In the early 1500’s, voyages of expedition were taking place around the world (leading to the discovery of many new plants and animals that were before unknown).

10. The 16th Century • With all of the new plants and animals that were being discovered, many scientists wanted a systematic way to name and classify them. • Many of the botanists were also physicians who were trying to find new medicines.

11. Andrea Cesalpino1519-1603 • Italian physician • Created one of the first new systems of classification since Aristotle • De Plantis(On Plants) • Classification was based on the structure of the plant’s fruits and seeds, created what we now know as “genera”

12. GaspardBauhin1560-1620 • Swiss physician • Described and named over 6,000 species of plants based on their “natural affinities” • His system was most likely the inspiration for binomial nomenclature, because he generally used only one descriptive word for each species

13. Confusion • By the end of the 1600’s, multiple systems existed for the classification of plants. • Depending on which system of classification a scientist used, the same plant could have multiple names. • This was very confusing, especially when trying to use these plants for medicine.

14. Carolus Linnaeus1707-1778 • Extremely influential Swedish botanist and physician • The father of modern taxonomy • The System of Nature 1735 • Organized plants and animals from Kingdoms down to Species, basing this on their shared physical characteristics

15. Carolus Linnaeus1707-1778 • Species Plantarum1753 • Introduced Binomial Nomenclature (recognizing an organism by it’s genus and species). Ex: Homo sapiens • He also included a complete list of all plant genera and species known to him at the time

16. “God Created, Linnaeus Named” • Up until the late 1800’s, Linnaean taxonomy persisted with minimal changes • The theory of the day was that “God created, Linnaeus named” • Until this point, organisms were categorized by their shared physical characteristics, and not by their evolutionary relationships

17. August Wilhelm Eichler1839-1887 • German botanist • Divided plants into non-floral and floral plants • The first to use evolutionary relationships in taxonomy

18. Charles Darwin (1809-1882) The shift from traditional taxonomy to cladistics first occurred after evolution and natural selection were proposed by Charles Darwin in The Origin of Species. (1859)

19. Cladistics • The classification of species into groups which are based on their evolutionary relationships. • Monophyletic groups consist of an ancestor and ALL of its descendants. • Cladistics differs from the mechanisms of classification before it because it is based on derived characteristics.

20. Cladogram

21. Shared Ancestry • Cladistic taxonomy is based on shared characteristics that are inherited from a common ancestor . These characteristics include: • Anatomical structures • Patterns of embryonic development

22. DNA Since the birth of molecular biology, similarities between organisms can be compared at the protein and DNA level (making cladistic taxonomy more precise than ever).

23. Phylocode • The International Code of Phylogenetic Nomenclature • A movement to change the nomenclature away from the Linnaean system, to one where the evolutionary relationships between organisms are better represented.

24. Example • Class: Mammalia • Current definition: The highest class of vertebrate. Warm-blooded. The young are nourished for a time by milk, or an analogous fluid, secreted by the mammary glands of the mother. • Possible Phylogenetic definition: the clade originating with the most recent common ancestor of Homo sapiens and Ornithorhynchusanatinus.

25. Phylocode? • The movement has inspired a lot of controversy and hostility. • As of right now, it is generally considered an unstable substitute for the Linnaean system. • Future?